Over 23 million surgeries are performed each year in the United States. Currently there are no objective measures for pain during surgery. Over the past few years we have developed the use of Near Infrared Spectroscopy (NIRS) to provide an objective measure of pain sensation. Near infrared spectroscopy (NIRS) systems are simple and portable, and easily applicable in the operating room, enabling the physician to measure activity in specific brain regions involved in the sensation of pain (primary somatosensory cortex, SI) or motor planning/escape (supplementary motor cortex, SMA). We have identified a specific pain signal from the supplementary motor and prefrontal cortices. We now propose to advance the NIRS technology to make the measure of this pain biomarker more robust for the clinical environment, validate the measure in controlled clinically relevant conditions, and then demonstrate clinical utility for monitoring pain sensation in an operating room environment. Our hypothesis is that objective measures by NIRS during anesthesia of neural activity in the primary somatosensory and prefrontal cortices in response to an intermittent pain stimulus will reflect the effectiveness of analgesic blockade while under anesthesia. Three specific aims have been generated to test this hypothesis: (1) To advance NIRS technology for the operating room environment by advancing signal processing to filter systemic interference and dynamically estimate the pain biomarker; (2) To validate objective measure of pain by evaluating analgesic effects of an opioid (morphine) in healthy men and women; and to test for pain measures under sedation in otherwise healthy men and women undergoing colonoscopy; and (3) To translate these measures to patients undergoing inhalational anesthesia or total intravenous anesthesia. Successful completion of the aims will lead towards a new tool for the anesthesiologist to optimize management of the patient to reduce the incidence of peri-operative pain-related sequelae. We have put together an interdisciplinary team (NIRS specialists and pain specialists and physicians) to undertake and complete the proposed studies.